What does it mean these artists are underappreciated?It means that for what they have in their galleries, they deserve much more attention. This doesn't mean they are generally underappreciated, but on dA - yes.

Where do you find all these people?Often they're my watchers - I check out every user who adds me. Also, I'm a creepy stalker and look through other people's favourites. And group galleries.

Can I suggest a gallery for your feature?Of course. Please send me a note with a link (not in a comment!). It may take a couple of posts before your suggestion is shown, though, I always have some (-404)'s drafted and waiting in sta.sh.